{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,14]],"date-time":"2026-01-14T00:27:01Z","timestamp":1768350421016,"version":"3.49.0"},"reference-count":51,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2012,1,16]],"date-time":"2012-01-16T00:00:00Z","timestamp":1326672000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Particle separation is of great interest in many biological and biomedical applications. Flow-based methods have been used to sort particles and cells. However, the main challenge with flow based particle separation systems is the need for a sheath flow for successful operation. Existence of the sheath liquid dilutes the analyte, necessitates precise flow control between sample and sheath flow, requires a complicated design to create sheath flow and separation efficiency depends on the sheath liquid composition. In this paper, we present a microfluidic platform for sheathless particle separation using standing surface acoustic waves. In this platform, particles are first lined up at the center of the channel without introducing any external sheath flow. The particles are then entered into the second stage where particles are driven towards the off-center pressure nodes for size based separation. The larger particles are exposed to more lateral displacement in the channel due to the acoustic force differences. Consequently, different-size particles are separated into multiple collection outlets. The prominent feature of the present microfluidic platform is that the device does not require the use of the sheath flow for positioning and aligning of particles. Instead, the sheathless flow focusing and separation are integrated within a single microfluidic device and accomplished simultaneously. In this paper, we demonstrated two different particle size-resolution separations; (1) 3 \u00b5m and 10 \u00b5m and (2) 3 \u00b5m and 5 \u00b5m. Also, the effects of the input power, the flow rate, and particle concentration on the separation efficiency were investigated. These technologies have potential to impact broadly various areas including the essential microfluidic components for lab-on-a-chip system and integrated biological and biomedical applications.<\/jats:p>","DOI":"10.3390\/s120100905","type":"journal-article","created":{"date-parts":[[2012,1,16]],"date-time":"2012-01-16T11:14:14Z","timestamp":1326712454000},"page":"905-922","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":92,"title":["Sheathless Size-Based Acoustic Particle Separation"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4368-2238","authenticated-orcid":false,"given":"Rasim","family":"Guldiken","sequence":"first","affiliation":[{"name":"Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA"}]},{"given":"Myeong Chan","family":"Jo","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA"}]},{"given":"Nathan D.","family":"Gallant","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA"}]},{"given":"Utkan","family":"Demirci","sequence":"additional","affiliation":[{"name":"Center for Biomedical Engineering, Department of Medicine, Brigham and Women\u2019s Hospital, Harvard Medical School, Boston, MA 02115, USA"},{"name":"Harvard-MIT Health Sciences and Technology, Cambridge, MA 02139, USA"}]},{"given":"Jiang","family":"Zhe","sequence":"additional","affiliation":[{"name":"Department of Mechanical Engineering, University of Akron, Akron, OH 44325, USA"}]}],"member":"1968","published-online":{"date-parts":[[2012,1,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Moon, S., Gurkan, U.A., Blander, J., Fawzi, W.W., Aboud, S., Mugusi, F., Kuritzkes, D.R., and Demirci, U. (2011). Enumeration of CD4(+) T-cells using a portable microchip count platform in tanzanian HIV-infected patients. PLoS One.","DOI":"10.1371\/journal.pone.0021409"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"357","DOI":"10.1016\/j.actatropica.2003.11.009","article-title":"Microfluidic approaches to malaria detection","volume":"89","author":"Gascoyne","year":"2004","journal-title":"Acta Trop"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"065004:1","DOI":"10.1088\/0960-1317\/21\/6\/065004","article-title":"A microfluidic multichannel resistive pulse sensor using frequency division multiplexing for high throughput counting of micro particles","volume":"21","author":"Jagtiani","year":"2011","journal-title":"J. Micromech. Microeng"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1088\/0960-1317\/17\/2\/017","article-title":"A micromachined high throughput coulter counter for bioparticle detection and counting","volume":"17","author":"Zhe","year":"2007","journal-title":"J. Micromech. Microeng"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1241","DOI":"10.1007\/s10404-010-0627-y","article-title":"Real-time monitoring of wear debris in lubrication oil using a microfluidic inductive Coulter counting device","volume":"9","author":"Du","year":"2010","journal-title":"Microfluid. Nanofluid"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1233","DOI":"10.1039\/b509386d","article-title":"Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics","volume":"5","author":"Yamada","year":"2005","journal-title":"Lab Chip"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"637","DOI":"10.1007\/s10544-007-9055-5","article-title":"Microfluidic devices for size-dependent separation of liver cells","volume":"9","author":"Yamada","year":"2007","journal-title":"Biomed. Microdevices"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"987","DOI":"10.1126\/science.1094567","article-title":"Continuous particle separation through deterministic lateral displacement","volume":"304","author":"Huang","year":"2004","journal-title":"Science"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"046304","DOI":"10.1103\/PhysRevE.78.046304","article-title":"Multidirectional sorting modes in deterministic lateral displacement devices","volume":"78","author":"Long","year":"2008","journal-title":"Phys. Rev. E"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"818","DOI":"10.1039\/b802268b","article-title":"Pinched flow fractionation devices for detection of single nucleotide polymorphisms","volume":"8","author":"Larsen","year":"2008","journal-title":"Lab Chip"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"5465","DOI":"10.1021\/ac049863r","article-title":"Pinched flow fractionation: Continuous size separation of particles utilizing a laminar flow profile in a pinched microchannel","volume":"76","author":"Yamada","year":"2004","journal-title":"Anal. Chem"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1369","DOI":"10.1021\/ac061542n","article-title":"Gravity-driven microfluidic particle sorting device with hydrodynamic separation amplification","volume":"79","author":"Huh","year":"2007","journal-title":"Anal. Chem"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"3038","DOI":"10.1039\/b912547g","article-title":"Inertial microfluidics","volume":"9","year":"2009","journal-title":"Lab Chip"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2973","DOI":"10.1039\/b908271a","article-title":"Inertial microfluidics for continuous particle separation in spiral microchannels","volume":"9","author":"Kuntaegowdanahalli","year":"2009","journal-title":"Lab Chip"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"223902","DOI":"10.1063\/1.3036898","article-title":"Lateral-driven continuous magnetophoretic separation of blood cells","volume":"93","author":"Jung","year":"2008","journal-title":"Appl. Phys. Lett"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1039\/B514539B","article-title":"Paramagnetic capture mode magnetophoretic microseparator for high efficiency blood cell separations","volume":"6","author":"Han","year":"2006","journal-title":"Lab Chip"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1003","DOI":"10.1007\/s10404-010-0616-1","article-title":"Continuous separation of non-magnetic particles inside ferrofluids","volume":"9","author":"Zhu","year":"2010","journal-title":"Microfluid. Nanofluid"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1039\/C1LC20864K","article-title":"Ferrofluid mediated nanocytometry","volume":"12","author":"Kose","year":"2012","journal-title":"Lab Chip"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1732","DOI":"10.1039\/b821508a","article-title":"EWOD-driven droplet microfluidic device integrated with optoelectronic tweezers as an automated platform for cellular isolation and analysis","volume":"9","author":"Shah","year":"2009","journal-title":"Lab Chip"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1038\/nature02144","article-title":"Microfluidic sorting in an optical lattice","volume":"426","author":"MacDonald","year":"2003","journal-title":"Nature"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1162","DOI":"10.1088\/0960-1317\/16\/7\/008","article-title":"A 3D paired microelectrode array for accumulation and separation of microparticles","volume":"16","author":"Chen","year":"2006","journal-title":"J. Micromech. Microeng"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1973","DOI":"10.1002\/1522-2683(200207)23:13<1973::AID-ELPS1973>3.0.CO;2-1","article-title":"Particle separation by dielectrophoresis","volume":"23","author":"Gascoyne","year":"2002","journal-title":"Electrophoresis"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"134101","DOI":"10.1063\/1.3238313","article-title":"Double aperture focusing transducer for controlling microparticle motions in trapezoidal microchannels with surface acoustic waves","volume":"95","author":"Tan","year":"2009","journal-title":"Appl. Phys. Lett"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Kapishnikov, S., Kantsler, V., and Steinberg, V. (2006). Continuous particle size separation and size sorting using ultrasound in a microchannel. J. Stat. Mech.","DOI":"10.1088\/1742-5468\/2006\/01\/P01012"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1039\/B313493H","article-title":"Acoustic control of suspended particles in micro fluidic chips","volume":"4","author":"Nilsson","year":"2004","journal-title":"Lab Chip"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1537","DOI":"10.1039\/B612064B","article-title":"Ultrasonic standing wave manipulation technology integrated into a dielectrophoretic chip","volume":"6","author":"Wiklund","year":"2006","journal-title":"Lab Chip"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1139","DOI":"10.1039\/b704965j","article-title":"Single cell epitaxy by acoustic picoliter droplets","volume":"7","author":"Demirci","year":"2007","journal-title":"Lab Chip"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1103\/RevModPhys.83.647","article-title":"Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics","volume":"83","author":"Friend","year":"2011","journal-title":"Rev. Mod. Phys"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1572","DOI":"10.1016\/j.athoracsur.2004.04.071","article-title":"Particle separation using ultrasound can radically reduce embolic load to brain after cardiac surgery","volume":"78","author":"Jonsson","year":"2004","journal-title":"Ann. Thorac. Surg"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"225","DOI":"10.1039\/b209030a","article-title":"An acoustic wave sensor incorporated with a microfluidic chip for analyzing muscle cell contraction","volume":"128","author":"Li","year":"2003","journal-title":"Analyst"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"5117","DOI":"10.1021\/ac070444e","article-title":"Free flow acoustophoresis: Microfluidic-based mode of particle and cell separation","volume":"79","author":"Peterson","year":"2007","journal-title":"Anal. Chem"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1039\/B716321E","article-title":"Focusing microparticles in a microfluidic channel with standing surface acoustic waves (SSAW)","volume":"8","author":"Shi","year":"2008","journal-title":"Lab Chip"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"47003","DOI":"10.1209\/0295-5075\/87\/47003","article-title":"Rapid fluid flow and mixing induced in microchannels using surface acoustic waves","volume":"87","author":"Tan","year":"2009","journal-title":"Europhys. Lett"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1088\/0960-1317\/16\/3\/009","article-title":"Active micro-mixers using surface acoustic waves on Y-cut 128 degrees LiNbO3","volume":"16","author":"Tseng","year":"2006","journal-title":"J. Micromech. Microeng"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"104103","DOI":"10.1063\/1.2889951","article-title":"Acoustic-counterflow microfluidics by surface acoustic waves","volume":"92","author":"Cecchini","year":"2008","journal-title":"Appl. Phys. Lett"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1557","DOI":"10.1039\/b803967d","article-title":"Polydimethylsiloxane-LiNbO3 surface acoustic wave micropump devices for fluid control into microchannels","volume":"8","author":"Girardo","year":"2008","journal-title":"Lab Chip"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"2319","DOI":"10.1039\/c1lc20042a","article-title":"Three-dimensional continuous particle focusing in a microfluidic channel via standing surface acoustic waves (SSAW)","volume":"11","author":"Shi","year":"2011","journal-title":"Lab Chip"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"789","DOI":"10.1039\/b915522h","article-title":"Surface acoustic wave actuated cell sorting (SAWACS)","volume":"10","author":"Franke","year":"2010","journal-title":"Lab Chip"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"234106:1","DOI":"10.1063\/1.3524511","article-title":"Unique flow transitions and particle collection switching phenomena in a microchannel induced by surface acoustic waves","volume":"97","author":"Tan","year":"2010","journal-title":"Appl. Phys. Lett"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"3354","DOI":"10.1039\/b915113c","article-title":"Continuous particle separation in a microfluidic channel via standing surface acoustic waves (SSAW)","volume":"9","author":"Shi","year":"2009","journal-title":"Lab Chip"},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Strege, M.A., and Lagu, A.L. (2004). Capillary Electrophoresis of Proteins and Peptides, Humana Press.","DOI":"10.1385\/159259798X"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"2890","DOI":"10.1039\/b910595f","article-title":"Acoustic tweezers: Patterning cells and microparticles using standing surface acoustic waves (SSAW)","volume":"9","author":"Shi","year":"2009","journal-title":"Lab Chip"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1007\/s10404-011-0798-1","article-title":"Size-dependent microparticles separation through standing surface acoustic waves","volume":"11","author":"Nam","year":"2011","journal-title":"Microfluid. Nanofluid"},{"key":"ref_44","first-page":"167","article-title":"Acoustic radiation pressure on a compressible sphere","volume":"5","author":"Yosioka","year":"1955","journal-title":"Acustica"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"492","DOI":"10.1039\/B601326K","article-title":"Chip integrated strategies for acoustic separation and manipulation of cells and particles","volume":"36","author":"Laurell","year":"2007","journal-title":"Chem. Soc. Rev"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"280","DOI":"10.1007\/s10404-005-0033-z","article-title":"Hydrodynamic focusing for vacuum-pumped microfluidics","volume":"1","author":"Stiles","year":"2005","journal-title":"Microfluid. Nanofluid"},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Gardner, J.W., Varadan, V.K., and Awadelkarim, O.O. (2001). Microsensors, MEMS, and Smart Devices, John Wiley & Sons.","DOI":"10.1002\/9780470846087"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"871","DOI":"10.1039\/B516401J","article-title":"A microfluidic device for continuous, real time blood plasma separation","volume":"6","author":"Yang","year":"2006","journal-title":"Lab Chip"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"7434","DOI":"10.1073\/pnas.0712398105","article-title":"Hydrodynamic metamaterials: Microfabricated arrays to steer, refract, and focus streams of biomaterials","volume":"105","author":"Morton","year":"2008","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"655","DOI":"10.1039\/b515371a","article-title":"Critical particle size for fractionation by deterministic lateral displacement","volume":"6","author":"Inglis","year":"2006","journal-title":"Lab Chip"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"013510:1","DOI":"10.1063\/1.3068750","article-title":"Efficient microfluidic particle separation arrays","volume":"94","author":"Inglis","year":"2009","journal-title":"Appl. Phys. Lett"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/12\/1\/905\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:48:29Z","timestamp":1760219309000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/12\/1\/905"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2012,1,16]]},"references-count":51,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2012,1]]}},"alternative-id":["s120100905"],"URL":"https:\/\/doi.org\/10.3390\/s120100905","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2012,1,16]]}}}